1. Field of the Invention
The present invention relates to a rotary head type magnetic recording/reproducing device, more especially relates to a rotary head type magnetic recording/reproducing device used in VTR (video tape recorder), DAT (digital audio tape recorder), a data recorder and a back-up streamer each having a rotary head.
2. Description of the Related Art
A rotary head type magnetic recording/reproducing device according to the related art comprises a lower stationary drum, a motor having a rotary shaft penetrating the stationary drum, and an upper rotary drum disposed coaxially with the stationary drum and secured to the rotary shaft of the motor.
An opening for accommodating a magnetic head is formed on an outer surface of the rotary drum at a position adjacent to the lower end of the rotary drum, thus the magnetic head is mounted within the opening. A stepped portion for guiding a magnetic tape is formed in an outer surface of the stationary drum.
In order to conduct the recording/reproducing by bringing the magnetic head into directly contact with the magnetic tape, the magnetic head radially projects over the outer surface of the rotary drum. The rotary drum is arranged to have the same outer diameter from the top end thereof to the lower end thereof, the rotary drum being greater in diameter than the stationary drum by a certain degree.
The magnetic tape is arranged to come into contact with both the rotary drum and the stepped portion formed in the stationary drum.
However, the above-described device encounters the following problems:
A contact pressure between the magnetic tape and the rotary drum is greater than a contact pressure between the magnetic tape and the stationary drum. The contact pressure between the magnetic tape and the rotary drum increases when it approaches the stationary drum.
The magnetic tape is bent in its widthwise direction since the contact pressure becomes maximal in a portion in which the magnetic tape comes contact with the magnetic head. Furthermore, a vacuum pressure is generated in a gap between the magnetic head and the opening, the vacuum pressure causing the magnetic tape to be sucked in the direction toward the center of the rotary drum. Accordingly, the magnetic tape is warped in its lengthwise direction, causing the magnetic powder to be separated from the magnetic tape. The separated magnetic powder can contaminate the surface of the magnetic head. As a result, the recording/reproducing performance of the device of this type deteriorates. Furthermore, the magnetic tape can be damaged during its contact with a corner portion of the rotary drum defining the opening. The magnetic tape loses its durability due to the damage.